1. Field of the Invention
The present invention relates to a cage for bearing used in a bearing such as a swivel seat bearing, and in more detailed to a cage for bearing, which is formed by connecting plural plate-like members in a cylindrical shape, and a bearing using the same.
2. Description of the Related Art
A swivel seat bearing, includes members called separators that are interposed between respective balls in order to prevent the balls adjoining in circumferential direction from directly contacting each other, without using the cage. This type of bearing is difficult to be assembled and, further, the separators interfere with the rotation of the balls, so that a rotational torque becomes large.
Contrary to this, the swivel seat bearing of a type in which a usual cylindrical cage used in radial ball bearing is utilized is easy to be assembled and its rotational torque is reduced as well.
However, if a diameter of the swivel seat bearing becomes large, for the conventional cylindrical cage, its wall thickness becomes very thin and it becomes flexible owing to its insufficient rigidity, so that its roundness becomes extremely low and thus it cannot be used.
Further, there is known a cage formed into an approximately cylindrical shape by continuously arranging plural plate-like pieces in a circumferential direction. It is necessary that each of the plate-like pieces constituting this cage has a shape warped like a bow when viewed from the side. This warped shape is obtained by a direct replica from metal die molding the plate-like member. In this case, in order to prevent an unnecessary distortion deformation after the molding, the plate-like member is adapted such that the distortion deformation after the molding does not occur as far as possible by using a hard material or mixing reinforcing fibers as the plate-like member.
For the cage consisting of such plate-like members, since it is necessary to mold the plate-like member into a special shape worked into the bow shape by the metal die, costs for designing and manufacturing the metal die become high, so that a manufacturing cost of the cage becomes high.
Moreover, in case of the cage consisting of the plate-like members, in order to change its diametric dimension in large or small size, it is necessary to prepare a plurality of molding metal dies for its exclusive use, since it is necessary to change a warp degree of the plate-like member. Thus, equipment cost is greatly increased.